Effect of Some Growth Regulators and Nutritional Compounds as Substitutes for Chilling of ‘Delicious’ Apple Leaf and Flower Buds

Abstract

Rest of ‘Delicious’ apple (Malus domestica Borkh.) buds was satisfied partially by applications of 6-ben-zylamino purine + gibberellic acid (BA+GA4+7 = Promalin), BA alone, potassium nitrate, and thiourea; GA4+7 alone had no effect. The combination of thiourea and potassium nitrate was as effective as Promalin or BA in stimulating flower bud development. Potassium nitrate had a pronounced effect on forcing flower buds while thiourea had more effect on forcing vegetative buds. BA and Promalin affected both flower and vegetative buds. No treatment affected bloom date or growing degree hours (GDH) required for flower bud expansion under our conditions when applied after 450, 950, or 1200 hours of chilling. Promalin and BA were both effective at 300 and 500 ppm, while thiourea and potassium nitrate were effective at 2% and 3% (w/v), respectively.